35986-44-8Relevant articles and documents
PHOTOCHEMISTRY OF DIENONES-VIII; THE LOW TEMPERATURE PHOTOCHEMISTRY OF (Z)-β-IONONE AND ITS PHOTO-ISOMERS
Cerfontain, Hans,Geenevasen, Jan A. J.
, p. 1571 - 1576 (1981)
The isomerizations of (E)-β-ionone 1, and of mixtures of the isomeric pyran 2 and (Z)-β-ionone 3 in CD3OD as solvent on direct irradiation with λ 254 nm and on triplet photo-sensitization have been studied at temperatures 24:Φ34=0.50.On starting with either 1 or mixtures of 2 and 3 the same photo-stationary equilibrium ratio of 1-3 is eventually obtained, viz 1:2:3=17:72:11. 4 is photostable relative to 1-3.The perdeuterobenzophenone triplet photo-sensitization with λ 366 nm at -50 deg C of 1 leads to 3 as the sole primary product, which isomer on triplet sensitization yields both 1 and 2.The triplet sensitized conversion is much faster for (Z)- than (E)-β-ionone.On starting with either 1 or mixtures of 2 and 3, eventually the same photo-stationary state is obtained, viz 1:2:3=39:46:15. (Z)-retro-γ-ionone 4 is not formed in the triplet sensitized irradiations of 1, 2 and 3 and in the direct irradiation it apparently results from the singlet excited state of the three substrates.The UV spectrum of the (unstable) (Z)-β-ionone 3 has been indirectly determined; its absorption occurs at lower wavelength and is of lower intensity than that of the (E)-isomer 1.
